Identification of iron transition group trace impurities in GaN bulk crystals by electron paramagnetic resonance

Abstract

We report on the observation of electron paramagnetic resonance of iron, manganese and nickel trace impurities in bulk GaN crystals grown by the sublimation sandwich method. The resolved hyperfine structure due to interaction with 55Mn ( I = 5 2 ) nuclei has been observed in GaN, allowing unambiguous identification of the impurity. Manganese and nickel exist in Mn 2+ (3 d 5) and Ni 3+ (3 d 7) charge states with electron spin S = 5 2 and S = 3 2 , respectively, and occupy gallium sites in the GaN lattice. For Mn 2+ we found g = 1.999, hyperfine structure constant A = 70.10 −4 cm −1 and fine structure parameter / D/ = 240.10 −4 cm −1. The EPR spectrum of Ni 3+ in GaN had the characteristic anisotropy of an S = 3 2 system in a strong axial crystalline field. The effective g-factor values were found to be g′ ∥ = 2.10 and g′ ⊥ ≅ 4.20 for a system with an effective spin S′ = 1 2 . An analogy was revealed between the parameters of Mn 2+ and Ni 3+ in GaN and ZnO crystals. The zero-phonon line at 1.047 eV seems to belong to transition 4 T 2( F)- 4 A 2( F) within 3 d levels of Ni 3+ ion with a 3 d 7 electronic configuration.